NEW DELHI â€” Indians have become much more unhappy about their lives in the past four years despite one of the worldâ€™s fastest rates of economic growth, a survey by the Gallup polling organization showed Monday.

The deterioration appears driven partly by the expectation, created by politicians and the media, that Indiaâ€™s boom would dramatically improve its citizensâ€™ standard of living.

When many Indians realized that the boom was not significantly benefiting them, their sense of well-being and optimism about the future seemed to collapse.

â€œIt is very dangerous to create expectations and not meet them,â€ said Rajesh Srinivasan, Gallupâ€™s regional research director for Asia and the Middle East.

The number of Indians who rated their lives poorly enough to be considered â€œsufferingâ€ rose this year to 31 percent, equivalent to 240 million people, a dramatic rise from just 7 percent in 2008, Gallupâ€™s surveys showed.

It is also significantly higher than the global average of 13 percent in the Washington-based polling organizationâ€™s 2011 survey of 150 countries.

Gallup classifies respondents as â€œthriving,â€ â€œstrugglingâ€ or â€œsufferingâ€ according to how they rate their current and future lives. While 74 percent of Danes said they were â€œthriving,â€ the highest percentage anywhere in the world, just 13 percent of Indians said the same thing. The global average is 24 percent.

Indiaâ€™s self-image has taken a battering in the past few years. Corruption scandals dominate the headlines on a daily basis, the government seems paralyzed and unable to take even simple steps to reform the economy, and growth has been slowing.

The sense that the 21st century belonged to India has begun to evaporate, replaced by a deepening sense of malaise. Business confidence and investment have also declined.

Massive government welfare and rural employment programs have helped drive down poverty levels, the Gallup survey found. The share of people saying they did not have enough money for food dropped to 13 percent in 2012 from 35 percent in 2006.

But high levels of inflation have helped depress Indiansâ€™ sense of financial well-being. Stress levels have risen, and the number of people who can count on social support and help has fallen. The percentage of those saying they had smiled or laughed the previous day fell to 52 percent in 2012 from 62 percent in 2006.

Even more worrying was that levels of well-being and optimism were no higher among 15- to 24-year-olds, at a time when India is hoping to reap a â€œdemographic dividendâ€ in the form of faster economic growth as a result of a bulge in its population of young people. Just 15 percent of people in that age group said they were â€œthrivingâ€ in 2012, scarcely better than the average for the country as a whole.

â€œIn most countries, 15- to 24-year-olds are the most optimistic,â€ said Srinivasan. â€œIt is very, very depressing to see those numbers are so low.â€

The findings also raise the possibility of the sort of social unrest that struck Los Angeles 20 years ago after police officers were filmed beating Rodney King, or the sort of upheavals that struck Tunisia and Egypt last year, said Jim Clifton, Gallupâ€™s chairman and chief executive officer. â€œAll you need is a matchstick event,â€ he said.

Srinivasan agreed that Indiaâ€™s failure to meet the aspirations of its young people through better education and good jobs could mean more youths â€œlooking for trouble,â€ and he said similar levels of perceived suffering had led to â€œtransformation revolutionsâ€ in other countries.

â€œBut I wouldnâ€™t forecast something like that for India,â€ he said, arguing that freedom of expression here helps to defuse tensions.

While Gallupâ€™s findings refer to individual Indiansâ€™ sense of personal well-being, the results are mirrored by a distinct deterioration in the national mood here in the past few years, as well as a decline in the optimism that powered the Indian story.

In recent weeks, the countryâ€™s self-image has continued to take more body blows, with accusations of corruption in the armed forces, one of Indiaâ€™s most respected institutions, and allegations that the president has abused his power.

The ratings agency Standard and Poorâ€™s cut its outlook for India to negative and warned of a possible downgrade in the countryâ€™s debt rating as a result of high levels of government borrowing and â€œthe current political gridlock.â€

Ruchir Sharma, chief global economist of the Morgan Stanley financial services firm, reinforced the new skepticism surrounding India with the launch of his book â€œBreakout Nationsâ€ here last week.

In it, he argues that the hype around the so-called BRIC economies of Brazil, Russia, India and China is overblown, and he warns that India should not take its economic â€œdestinyâ€ for granted.

Even some of the most enthusiastic drumbeaters for India, including public relations consultant Suhel Seth, have changed their tunes in recent years. They have warned that â€œBrand Indiaâ€ has taken a beating because of â€œself-servingâ€ politicians and bureaucrats.

â€œThe India story is downhill and needs surgery, not beating about the bush as we are wont to do,â€ Seth wrote this week.

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